Means for controlling electrically-driven centrifugal machines.



G. A ADAMS. MEANS FOR CONTROLLING ELEOTRIOALLY DRIVEN GENTRIFUGALMACHINES. APPLICATION FILED APR. 3 1907v 2 SHEETS-SHEET 1.

mereidow A f tffi zwmi/ @1 N" wmia/wi Patented Jan. 17, 1911.

J. A. ADAMS. MEANS FOR CONTROLLING ELECTRIGALLY DRIVEN OENTRIFUGALMACHINES.

APPLICATION FILED APILS, 1907 Patented Jan 1?, 1911.

2 SHBETS-SHEET 2.

UNITED srA'rEs PATENT omimE.

COMFORT A. ADAMS, 0F CAMBRIDGE, MASSACHUSETTS, ASSIGNOR T0 AMERICAN TOOL& MACHINE COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MASSA-CHUSETTS.

MEAIlS FOR CONTROLLING ELECTRICALLY-DRIVEN CENTRIFUGAL MACHINES.

Specification of Letters Patent. I Patentgd Jan, 1'7, 1911.

Application filed April 3, 1907. Serial No. 366,091.

To all whom it may concern:

Be it known that l, COMFORT A. ADAMS, citizen of the United States,'-andresident of Cambridge, Middlesex county, 'Massachusetts, have inventedcertainnew and use ful Improvements in Means for ControllingElectrically-Driven Centrifugal Machines, of which the following is aspecification.

This invention has relation to the control of electrically drivencentrifugal machines and is intended to provide a construction andarrangement whereby the machine may be quickly brought to a state ofrest from its full speed without undue heating of parts and also toprovide an advantageous arrangement for employing the driving motor forthe purpose of properly checking and arresting the revolution of themachine.

The conditions attending the operation of machines of this type arepeculiarly severe and exacting since in certain of its applications toindustrial purposes these machines when loaded Weigh upward of a ton andare rotated at a high rate of speed approxi mating 1100 revolutions ormore per minute.

When used in sugar houses the duration of actual run for each load isvery short, say from two to live m nutes. so that the. machine has to bestarted and stopped at very short intervals. Under such conditions thequickness and effectiveness in obtaining a maximum speed as well as inbringing the machine to a full stop a most important factor in theetlicienoy and value of the machine. To attain these resultsadvantageously and etl'ectively is the problem which this invention isintended tosolve.

Stated briefly and in genertl. terms the invention comprises thecombination with a centrifugal machine of an electric motor whoseshunt-wound field is connected with the two supply mains and whosearmature arranged in an open loop circuit has a direct connection withthe two mains, means bein provided for breaking the direct con nectionbetween the armature and one of the mains and for closing the loopcircuit to cause a reversal of the current through the armature. Meansare. also provided for cutting in a brake actuating coil for the purposeof assisting the reverse current 111 stoppmg the machine after saidreverse curi'cnt has decreased in strength owing to the slacking of'thearmature speed so that it exerts 'a relatively small force in stoppingthe machine.

In the accompanying drawings Figure l is an elevation partly in sectionillustrating a direct connected electrically driven centrifugal machineand its electromagnetic brake and switch by which the proper control ofthe machine is secured. Fig. 2 is a lan view of the braking members.Fig. 3 is an elevation of a detail of the brake shoe toggle levers. Fig.at is a diagrammatic view showing the different electrical connectionsand the course of the electric currents when the machine is starting andrunning normally. Fig. 5 is a diagrammatic view showing the electricalconnections as they are used to stop the machine.

The centrifugal machine itself may be of any suitable construction andin this case comprises a rotary basket supporting shaft (6 rotatablymounted in an oscillatory head a resting in the fixed hanger a andhaving connection with the motorshaft section 7) of the drivingshaft bymeans of any suitable form of flexible. coupling or joint (1.. T hemotor shaft Z to which the armature l) is secured extends through thesupporting hearing bracket 0 and has secured to its upper end the hollowbrake band or Wheel 6 inside of which are mounted the brake shoes 0which are pivoted to a Vertical pivoted post 0 extending upward from theframe C. The exterior of these brake shoes is provided with convexfriction faces or blocks adapted to engage the inner annular face of therotary brake band b i The free ends of the brake shoes 0 are engaged byoppositely disposed expansion or toggle levers whose adjacent endsengage a connecting link 0 to which is attachedtho depending pull ordraft rod 0. A retractile spring 0' serves to normally draw the brakeshoes toward each other out of engagement with the rotary brake wheel [2In this case I have shown the draft rodc connected to a the short end ofan actuating lever 1 which may be used as a hand lever and which hasalso an actuatingrod d provided-with an iron cylinder or core within thesolenoid d.

The motor here shown is of the multimains at the other end, the otherpole of the armature being connected directly with the other main sothat when the switch is closed the current will flow through both theseries field and the armature but when the connection is broken throughthe switch no current will flow in this direction from the series fieldto the armature.

The commutator g is of the continuous current type and should have itsbrushes adjusted to permit the, current to flow in either directionwithout sparking The circuit or conductor 6 of the shuntwound coils isprovided with a variable resistance and also with a bypass, connectionbeing made through the medium of the switch in such a way that duringthe normal running of the machine the current may be made to passthrough "any desired portion of the variable resistalice, while duringthe braking r-oeration of the machine this resistance may be entirelycut out by allowing the current to flow around the resistance throughthe by-pass. This will be more clearly understood by'ret'erence to Fig.4 which represents diagrammatically the ar- -rangement of theconnections during the normal operation of the machine. In this case theswitch 2' is thrown to the right and the current from the supply main isflowing through the conductors c, e and a through the resistance to thevshunt-wound coils of the field.

WVith the switch turned to the right as in Fig. & there will be a directflow of current from the positive to the negative main through theseries fields, the armature and the resistant-0'6 which is permanentlyconnected into the armature circuit. ()n the shifting of the switch tothe left however, as indicated in Fig. 5, this circuit is broken and asthe armature itself is included in the loop circuit 1') which is closedby the shifting of the switch to the left, the armature then runningunder the momentum of the machine will now act as a generator producinga flow of current in the reverse direc tion through the loop circuit b.In this loop circuit is interposed a small resistance 6 as shown.

lVith the switch thrown to the left the current through the conductor 0will flow to the shunt-wound coils of the field through and set thebrake.

the by-pass circuit a a passing around the entire variable resistanceand thus the current fiowin r through the circuit of the shuntwound fielcoils will be materially strengthened during the braking action so as tomore than com nsate for the cutting out of the series field during thebraking period.

The solenoid (l which is 111 open circuit while the armature is indirect connection with the two mains of the machine, is brought intoaction and energized by the shifting of the switch to the left so thatitbegins to exert a pull upon the brake lever to expand In this case oneterminal of the solenoid is connected with the positive supply main,while the other terminal is connected with the loop armature circuit bThe effect of this arrangement is as follows: Upon throwing the switchfrom the position shown in Fig. 4 to the position of 'Fig. 5, the directflow of the current from the mains through the armature is cutoff and areverse current through the loop circuit which is closed thereby isproduced, the momentum HALF. which produces this current being at firstnearly equal to that of the supply mains and of course, opposite indirection. The work now done by the armature as a generator rotatingunder the momentum of the machine, serves to rapidly check the speed ofrotation and consequently to lower the E.M.F. of the armature. With thisdecreasing EMF. in the loop circuit the intensity of the current passingthrough the solenoid d is increased owing to the increase in thedifference of potential between the two terminals of said solenoid, sothat the solenoid acts with increasing strength upon the brakemechanism. By this principle of arrangement the initial braking actionis principally that exerted through the employment of the armature as agenerator but as the braking efi'ect exerted'in this way is diminishedrapidly by the slowing up of the armature, a correspondingly increasedforce is exerted by the electromagnetic brake toarrest the rotation ofthe machine.

The use of the resistance coil 0 in the shunt field circuit c serves toprevent too rent a rush of current through the shunt circuit during thestarting of the machine, wlyile the cutting out of this resistance inshiftingthe switch to stop the machine serves to strengthen the. shuntcurrent and thus compensate for the loss of the series winding which isthen cut out of circuit. The shunt field is much more serviceable duringbraking as it does not decrease with decreasing speed.

l/Vhile the use of the series coil is advantageous inthat it strengthensthe field during the period of greatest load, namely the startibg periodof the machine, it will be understood that the use of the series windingis not essential in the practice of this invention.

Tifilfn switch is in central position the extra resistance inshunt-field serves toavoid heatoperated by a common lever,siibstantially as described.

2. The combination with a centrifugal machine of a direct-connectedmotor having shunt-wound field coils in whose circuit is included avariable resistance. an armature arranged in an open loop circuit andhaving direct. connection with the supply mains. means for cutting offthepsupply current to the armature and causing a reverse current to flowthrough the loop circuit to counteract the rotation of the machine. andmeans for simultaneously increasing the strength of current in theshunt-wound field coils by cutting out the variable resistance includedin their circuit, the means for cutting off the current of the armatureand for strengthening the shunt field current. being controlled by acommon lever, substantially as described.

3. The combination with a centrifugal machine of a direct-connectedmotor whose armature is arranged in an open loop circuit and has directconnection with the supply mains, said motor having also compound-woundfield coils, means for cutting oft the supply of current from the mainsto the armature and to permit a counter-currentin the armature to flowthrough the loopcircuit, and means for simultaneously cutting out theseries wound coils of the field and strengthening the current flowingthrough the shunt-wound coils of the field. substantially as described.

4. The combination ofthe rotary driving shaft of a centrifugal machine.said shaft embracing a basket-carrying shaft,,and a rigidly mountedelectric motor shaft with which said basket shaft is flexibly connected.a brake mechanism connected with the motor shaft, a solenoid foractuating said brake mechanism when energized, a motor whose poles areenergized by a continuous current. electrical connections by which thesolenoid is energized and the flow of current to the armature isinterrupted and the armature itself is caused to act as a generator toproduce 1 reverse or counter current which shall centrifugal I cmtincluding said armature. a brake acturetard the rotation of the machine.substantially as described.

The combination of the driving shaft, a compound-wouud motor whosearmature is directly connected therewith, a loop cirating solenoidcircuit electrically connected with one of the mains and with said loopcircuit, and means for cutting off the flow of current through theseries field to the armature for closing said loop circuit and saidsolenoid circuit in order to produce a. counter current ,of diminishingstrength through the loop circuit and a solenoid energizing current ofincreasing strength, substantially as described.

6. The combination of the shaft, a compound-wound whose shunt circuitincludes stat, a loop circuit including said armature. a brake actuatingsolenoid circuit connected rotary driving electric motor 'with said loopcircuit. and means whereby the extra resistance in the shunt-wound coiland the series-wound coil may be cut out at the same time the loopcircuit and the solenoid circuit are closed to produce a reverse currentin the loop circuit of the armaturean extra rheoand to energize thesolenoid, substantially as described. I

7. The combination of the driving shaft, a direct-connected motor whosefield coils are included in a shunt circuit and wh0'se armature isincluded in a loop circuit, a brake-actuating electric circuit connectedwith one of the mains and with said loop circuit, and means for cuttingoff the flow of current from the mains to the armature and closing saidloop circuit and said brake circuit to produce a countercurrent ofdiminishing strength through the loop circuit and a current. ofincreasing strength through the brake circuit.

8. The combination of the driving shaft, a direct-connected motor whosearmature and field are arranged in parallel circuits, anelcctrically-actuated brake, means for short-circuiting the ,armature toproduce a reverse current from rthe armature. and

means for connecting he brake circuit with the supply mains and inseries with the shmt-circuitcd armature to permit a'direct current toflow through the brake circuit in opposition to the electromotiveforcegen erated by the armature whereby the decrease in speed ofrotation of the armature results in progressively strengthening theaction of the brake as the braking action of the reverse current in thearmature decreases.

9. The combination of the drive shaft, a

direct-connected motor whose armature is I n a. l included in a loopcircuit, an electrically act-uated brake, a switch control, connectionsbetween the supply mains, the armature, the

brake circuit, and the loop circuit, whereby through the shifting of theswitch a direct erated by the armature in order to cause the brake toact with increasing effect as the speed of rotation diminishes.

In witness whereof, I have hereunto set my hand, this first day ofApril, 1907.

COMFORT A. ADAMS.

In the presence of Geo. N. GODDARD, KATHARINE A. DUGAN.

I may be opposed to the reverse current gen- 15 I

